1. Field of the Invention
The present invention relates to a method of manufacturing a laser diode.
2. Description of the Related Art
Patent Document 1 (Japanese Unexamined Patent Application Publication No. 8-255949) discloses a distributed feedback (DFB) laser diode having a diffraction grating with periodic projections and recesses. In the method of manufacturing a laser diode described in the document, first, an active layer and a guide layer are grown on a GaAs substrate, and an alignment mark composed of a SiO2 film is formed on the guide layer. Next, a mask pattern for forming a diffraction grating at a predetermined position on the guide layer is formed with reference to the alignment mark, and the guide layer is etched using the mask pattern to form a diffraction grating. Then, a cladding layer is grown on the diffraction grating in such a manner that the diffraction grating is embedded. In this process, the alignment mark is also buried in the cladding layer. The document describes that, since the cladding layer composed of semiconductor crystals does not grow on the alignment mark composed of SiO2, the alignment mark can be observed even after the cladding layer is grown.